Minus the fact that roof came out before the cayman was even in prototype form.

I used to be a member of s2ki.com. The roof was conceived by Spoon's racing program who decided that the oem hardtop design, even in CF form, had shortcomings due to aerodynamics. They came up with that roof instead. They eventually decided to offer it to the public, as they do with most of their engines and aerodynamic parts.

In fact, if my memory is correct, isn't there a spoon racing s2000 in gran turismo 3?